Oxidation of lower aliphatic alcohols



July 11, 19.44.

Lane 1 I .D. c. HULL' 2,353,159

OXIDATION OF LOWER ALIPHATIC ALCOHOLS Filed June '29, 1942 IBJ W METERCONDENSER 27 STEAM f 9 z|- W samura 24 ,-OXIDATION UNIT r PACKED z y 22SCRUBBER RECEIVER fi RECEIVER r W: w

OXIDI'ZING MEDIUM DAVID HULL- INVENTOR BY ATTORN s Patented July 11,194} UNITED STATES PATENT omen OXIDATION OF LOWER ALIPHATIC ALCOHOLSDavid C. Hull. Kingsport, 'lenn., casino: to Eastman Kodak Company,Rochester, N. Y., a cor-,-

poraiion of New Jersey Application June 29, 1942, Serial No. 448,959

3 Claims.

relatively high temperatures such as 300 C. or

400 C. and the application of several steps. In other words, theoxidation either has not been direct, or ii there has been directconversion, the yields have been very low. For example, consideringprior art procedure for, converting ethanol to aceticacid, before myinvention-it was considered necessary to first dehydrogenate all of theethanol and thereafter the aldchydic dehydrogenation product wasconverted to the acid which, as can be seen, involves a num of steps.

Carrying out oxidation processes in accordance with the prior artpossesses a number of disadvantages exemplified, for example, by thestantially a single step. Still another object,

however, is to provide a .process which may also be applied to, not onlythe monohydroxy alcohols, but to the polyhydroxy alcohols and othersimilar organic compounds. Another and particular object of thisinvention is to provide a direct oxidation process which may be operatedat relatively low temperatures .and under ordinary pressure conditions,yet give very satisfactory yields of the desired oxidation products.

' Still another object is to provide a direct oxidation process for theconversion of alcohols to acids wherein the alcohol may be converted,not.

only to an acid having a number of carbon atoms corresponding to thenumber of carbon atoms in the alcohol. molecule, but also to a diflerentacid. A still further object is to provide a process which may beoperated under other than normal atmospheric conditions. namely, undereither superatmospherie or reduced ressures.

required use of relatively high temperatures.

Also there may in some instances be the disadvantage of polymerizationof the products of the starting materials accompanied by low yields andother losses.

In my companion application aforesaid I have described a process for amore direct oxidation of organic compounds. While the process of myapplication functions .very satisfactorily and gives good yields inrelatively few steps, it involves the utilization of metals having anatomic number from 25 to 29. It is, therefore, apparent that it isdesirable, particularly under present conditions, to develop a processin order that other metals may be employed and the process improved inother respects, as will be apparent from the description which'follows.

After further investigation I have found that there are certain othercatalytic materials which may be employed in direct oxidation processesin a manner akin to the procedure set forth in my companion-applicationwhich not only permits obtaining direct oxidation, but permitsthevaluable for the direct conversion of lower ali phatic alcohols tolower aliphatic acids in sub A further object is to provide a directoxidation process that may be applied to either alcohols alone ormixtures of alcohols and aldehydes,

or other types of mixtures. A still further object is to provide adirect, low-temperature oxidation process which maybe applied to variousmixtures of alcohols and aldehydes where in both the alcohol and thealdehyde are converted into useful oxidation products. Another object isto provide a direct oxidation process,

particularly adapted to the treatment of alcohols such as butyl alcoholand the like wherein, not only may butyric acid be obtained, butcontents of other acids.

A further object is to provide novel catalysts containing liquidsparticularly adapted for employment in the aforesaid types of processesfor the direct conversion of alcohols alone, or alcohols in variousadmixtures, into useful oxidation products. A still further object is toprovide methods for roducing the catalysts as well as for activating andutilizing the. catalysts.

As already indicated, prior to my invention, if an alcohol were to beoxidized it was generally first dehydrogenated and then thedehydrogenation products further treated. In any event prior artprocesses as applied to alcohols usually involve the utilization oftemperatures in excess of 300 C. which, not only requires substantialheat inputbut, due to the higher temperatures I have found that contraryto such procedure trolled feed supply it.

an organic compound, exemplified in particular by ahydroxy compound as alower aliphatic alcohol, may be directly oxidized at relatively lowtemperatures, even temperatures substantially below 100 (2., with any ofthe usual oxidizing mediums of which the commonest one, namely, air, maybe readily utilized in my .process.' Also my process, after it is placedin operation, does not usually. require any heat input features oftreating'various mixtures under different-conditions, will "be set forthin detail h'ere inafter.

While the oxidation procedure may be carried denser it into separator2|. This separator has attached thereto a receiver 22 for condensate anda branch conduit 28 through which noncondensables may be conducted tothe scrubber 24..

The aforementioned scrubber is provided with a receiver 26 at the lowerpart thereof and vent conduit 21 from the upper part thereof, which may.lead through a meter or other device for measuring and testing theeilluents.

There may also be associated with the apparatus thermometers or othertemperature con- I trolling devices or various exchangers for reout inthe apparatus described in the aforesaid 4 companion application228,822, new Patent No. 2,287,803, for convenienceof consideration andfor a better understanding of the present invention reference will bemade to the attached drawing. The attached figure may-be considered asemi-diagrammatic side elevation view showing a general apparatusarrangement which could be employed for carrying out my process.

Referring to the drawing, 2 represents an oxidation unit whichmaycomprise any of'several diiferentconstructions. For-example, the pre-;.

ferred external construction wou1d, in a large diameter unit, be inaccordance with Hasche Patent 2,159,988. However, the construction maybe a sieve plate column, bubble plate col-' umn. or other comparablearrangement for permitting the contact of an oxidizing medium containingfree oxygen with the material to be oxidized. In the unit shown in theattached figure the column merely comprises an elongated, open column ofrelatively narrow dimen sions. Attached to the lower part of the unit at8 and l, are cooling jackets provided with inlets for cooling medium asat l and I.

The upper part of the unit was provided with a similar Jacket I:however, in this Jacket, rather than cooling medium some heating mediummay be circulated in the event that high boiling components are beingdirectly oxidized or the reaction temperature is to be held lower thanthat which'would maintain a constant volume of cata lyst. Inasmuch asthe construction is substantially the same, however, the mechanicalconstruction would be approximately the same and an inlet provided at l,I, and l: outlets are provided at II, II, and I8.

. As indicated, if desired in place of the external Jackets, coils maybe included within the unit and in large-size units such arrangementwherein internal coils; or both coils and Jackets are employed, may bedesirable.

The lower part of the unit is provided with a plurality of inletconduits, namely, inlet conduit ll which is connected with atemperature-con- Also leading into the lower part of the unit is aninlet conduit II for oxidizing medium.

The upper part of the unit is provided with a drawofl conduit I! whichthrough cops covering heat or otherwise facilitating or renderingtheoperation of the process more economical, or permitting it to beoperated with automatic control. Hence, my invention is not to berestricted in these respects.

I have found that certain metal compounds, as for example, estersderived from the so-called platinum group metals and having atomicnumbers between 44-82, may be incorporated in acidic solutions and thatthese solutions will function as a catalyst medium for the directoxidation of organic compounds. That is, an alcohol alone or alcohol andother organic compounds to be oxidized, may be passed into a catalystsolution, as aforementioned, in the presence of oxidizing mediumcontaining free oxygen and that the alcohol may be directly oxidized toacid. as will be observable in greater detail from the specific exampleswhich follow. Referring to the various metals which may be employed inaccordance with my invention, there may be mentioned ruthenium, rhodium,palladium, osmium, iridium, and platinum.

In preparing catalyst solutions for use in the 7 present process anyconvenient source of the metal may be employed, such as salts, oxides orother derivatives thereof. Preferably, a derivative would be chosenwhich is easily soluble under conditions prevailing in the process. Forexample, assuming that it is desired to convert an alcohol such asethanol or butanol directly to the corresponding aliphatic acid, thederivative of the catalyst metal would preferably be chosencorresponding to this acid. Specifically,

in the instance of producing acetic acid, there may be employed metalcompounds such as'silver, mercury or lead acetates, depending upon theparticular metal or metals selected.

Further examples of metal derivatives which may be employed forproducing the catalyst solution are rhodium acetate and palladiumacetate.

while the aforementioned metal derivatives may be employed in variousorganic liquids, which are solvents therefor, for simplicity ofoperation and minimizing the necessity of complicated separations Iprefer to dissolve the catalyst compound in a liquid principallycomprised of one of the materials which is to be produced in theprocess. For example, in the event my process was to be applied inconverting butyl alcohol directly into butyric acid I would preferablydissolve the catalyst compounds in an allphatic acid such as butyricacid. However, propionic or acetic acid could also be used. However, forinitially preparing the catalyst solution other liquids couldbeemployed, as for example, organic esters and the like such as butyl orethyl acetate. v

In any event, irrespective of the exact metal compound and the liquidthat the compound is I accompanied by heating obtained in any convenientmanner such as by flowing a heating medium in the jackets or cells inassociation with the oxidation unit or by introducing heated air. Thetemperature of treatment, however, may vary from around 0. up to theboiling point of the particular liquid present. In other words thesolution is maintained under liquid phase conditions.

It is also preferred to incorporate the oxidizing medium into thecatalyst liquid under at least atmospheric pressure as this permits theinclusion of a larger amount of oxidizing medium and fully saturates thecatalyst liquid.

After the catalyst liquid containing a metal selected from the platinumgroup metals as specified above, has been treated and brought to astarting temperature, usually above room temperature, but below around100 C., the organic compound to be oxidized may be supplied to theprocess.

That is, referring to the attached drawing, the oxidation column 2 isfilled with the catalyst liquid comprising one or more platinum groupmetals as above specified dissolved in the solvent and maintained at thedesired temperature. The hydroxy compound to be oxidized is introducedinto the oxidation process through conduit i4 and the oxidizing medium,usually air (however, pure oxygen or ozone may be employed and appear torender the catalyst solution more active, but are not necessary), andthe compound oxidized to one or more desired oxidation products, as willbe described hereinafter.

Assuming that the oxidation product is a liquid, a portion thereofmay bevolatilized or pumped off through conduit it through the condenser i9where condensables are condensed out to be collected in receiver 12. Theunconsumed gases (as nitrogen when air is used in oxidizing medium)unoxidized organic compound and the like components, uncondensed, passthrough conduit 23 into scrubber 24 where they are recovered. While onlya single scrubbing unit ha been indicated, a plurality of such units maybe employed or other recovery devices utilized.

The operation of my process to convert a organic compound'such as butylalcohol to allphatic acids and the functioning of various of theplatinum group metals as abovespecified as catalysts is believed quiteclearly illustrated by the data appearing in the following table:

and at a temperature between 30 C. and 50 C. While a 2.5% to 4% catalystsolution has been indicated, the amount of catalyst may vary from asmall amount to a saturated solution, but in general the amount ofcatalyst will be maintained between 1% or 2% and 12%.

While the foregoing examples are illustrative of one of the preferredapplications of my process, my process may be operated with the variousother catalyst referred to and under various other conditions, as willbe apparent from the.

examples which follow:

Example IV In accordance with this "example a catalyst solution iscomposed of 1000 parts of acetic acid having dissolved therein 0.5 partof antimony acetate, 0.5 part of palladium acetate, 0.5 part of platinumacetate and 10.0 parts of stannous acetate. This solution is employed aspreviously described with a feed of 1000 grams of acetaldehyde and 500grams of n-butyl alcohol. On this ratio is obtained an average yield of10-175 grams of butyric acid and 0-50 grams of propionic acid as themajor products of the oxidation process. As in the preceding examplesthe process was operated so that the catalyst solution was maintained inthe liquid phase. However, in the ,instance of alcohol, as butylalcohol, it is possible,

if it is desired to operate with temperatures up to nearly 150 C., thata higher temperature can be employed aspressure is applied to thereaction. In this reaction some excess oxidizing medium (air) may besupplied to the reaction so that a content of oxygen was indicated inthe of! gases.

When ethyl alcohol or propyl alcohol is used in place of or in admixturewith butyl alcohol, lower temperatures may be employed. Furthermore, thepressure may be varied within rather wide limits without basicallychanging the process. Similarly, the catalyst may be employed as a saltor mixture of salts of any, organic acid or acids, or a mixture of themetals themselves may be employed. g

In the foregoing examples there was some al- .cohol left unchanged whichmay be recovered either in the scrubber or otherwise. As indicated,while at normal atmospheric pressure a-temperature under 100 C., and inmany instances between 30 C. and 50 C., appears to be quitesatisfactory, the process may be caused to operate even at temperaturesas low as --5 C. and up to the boiling point of the catalyst solution.

In preferred operation using, for example, the

air as an oxidant, this may be supplied under some pressure and ifdesired a rather substantial excess can be incorporated, although fornormal operations a slightexcess, merely so that a few per cent ofoxygen are indicated in the eiliuents,

would be employed. In the event of the use of other oxidants such asrelatively pure oxygen and ozone, smaller amounts are required and maybe supplied under substantial pressure for causing Wei ht ace de- Metolacetate I hyde fed Weight but d produced Percent conwlrlm pro 0 0 acids2 prop 0 0 acid produced Per cent conversion but 0 I}. giilver QT III.Lead 14.43 41.9 None them to fully permeate the entire catalystsolution.

- time.

While in certain of the foregoing examples we have indicated theutilization of butyl alcohol in admixture with acetaldehyde, acomparable mixture of ethyl alcohol and butyraldehydev may be processedin the same manner to obtain a mixture of acetic and butyric acids.Similar re'- marks apply to the employment of other mixtures of alcoholsand aldehydes. That is, ethyl alcohol may be processed in admixture withacetaldehyde to produce relatively pure acetic acid. Or, for example,propyl alcohol-may be processed in accordance with the present inventionin the presence of acetaldehyde, butyraldehyde, or propionaldehyde.However, inasmuch as acetaldehyde is in many instances most readilyavailable and has a low boiling point, it would preferably be employedalong with the other alcohols such as butyl alcohol, amyl alcohol, andthe like as representing the most economical procedure as well astending to lower the boiling points and permitting the functioning ofthe process at lowest temperatures.

As already indicated, the pressure may be varied over wide limitswithout basically changing the process. However, since the processfunctions satisfactorily under normal atmospheric. pres sures I preferto operate under such conditions except that in some instances, such asfor saturating the catalyst solution with oxygen, I may apply a fewpounds pressure up to 2 or 3 atmosspheres for this purpose. Also, asindicated, the process functions very well at ordinary temperatures of30 C. to 50 C. 'However, by raising the temperatures above the rangeindicated and applying some increased pressure, larger amounts ofalcohol may be converted per pass per unit of Under such procedure thealdehyde feed would be correspondingly reduced as the amount of alcoholfed was increased.

- As apparent from certain of the preceding examples one valuable aspectof the present inbe restricted in my invention-excepting insofar as isnecessitated by the prior art and the spirit of the appended claims.

, What I claim and desire to secure by Letters Patent of the UnitedStates is: i

l. A process for the direct oxidation of a lower aliphatic alcohol toobtain the corresponding aliphatic acid, which comprises treating asolution of a metal ion of a metal of the platinum group cohol andaldehyde by treating said solution with is maintained in the liquidphase, and subsea gaseous oxidizing medium, maintaining the temperatureof the solution of-catalyst, alcohol and aldehyde during its treatmentwith the gaseous oxidizing medium such that ,the solution a gaseousoxidizing medium to form a catalyst vention is that acids having fewercarbon atoms than the alcohol being oxidized may be directly producedand the proportion of these other acids to the acid having the samenumber 01' carbon atoms as the alcohol being oxidized may be varied bychoice of the particular catalyst, as apparent from Examples I, II, IIIandIV set forth above.

It is apparent from the foregoing that my invention is applicable to thedirect oxidation of the various organic compounds, particularly hydroxycompounds such as various alcohols. The foregoing examples are merelyillustrative of some of the materials to which my low temperature liquidphase process may be applied, but various other compounds, such ashydroxy alcohols exemplified by glycols, may be treated in a comparablemanner. Hence, I do not wish to solution, introducing material amountsof a lower aliphatic alcohol and a lower aliphatic aldehyde into theactivated catalyst solution, oxidizing the alcohol of the resultingolution of catalyst, alcohol and aldehyde by treating said solution witha gaseous oxidizing medium, maintaining the temperature of the solutionof catalyst, alcohol and aldehyde duringits treatment with the gaseousoxidizing medium such that the solution is maintained in the liquidphase at a temperature of from -5 to C. and subsequently recovering thealiphatic acid produced.

3. A process for the direct oxidation of a lower aliphatic alcohol toobtaiin the corresponding aliphatic acid, which comprises treating asolution of a palladium salt in an aliphatic acid with an aldehyde and agaseous oxidizing medium to

